Defrosting method and apparatus for refrigeration systems



Patented Oct. 17, 1'9`5 OFFICE DEFROSTING METHOD AND APPARATUS FORREFRIGERATION SYSTEMS Louis F. La Porte, Wellston, Mo., assigner toFrancis L. La Porte, San Bernardino, Calif.

Application October 11, 1948, Serial No. 53,839

The present invention relates generally to the defrosting of coolingunits, or evaporators, included in mechanical refrigeration systems, andis a continuation in part of my co-opending application, Serial No.732,742, filed March 6, 1947.

A satisfactory solution of the defrosting problem has long been soughtby refrigeration experts and engineers. Various automatic,semiautomatic, and manually controllable devices and methods haveheretofore been devised, in a vain effort to provide simple, yeteffective defrosting means.

Some of such methods and the apparatus associated therewith have beenpatented. However, for one reason or another, these have been foundwanting in many respects, and fraught with so many disadvantages that itseems the refrigeration industry generally has seen fit to discard them.

The primary object of the present invention y therefore. is to provide asimple method, and

simple apparatus, whereby the disadvantages inherent in the herebeforemethods are overcome.

In my said pending application there is disclosed a method and apparatusfor defrosting cooling units and the drain pans associated therewith.

Broadly, the method of defrosting therein set forth, includes theprovision of a closed, or airtight fluid system of heat-conductingmetallic material, which system after having been first evacuated, andthereupon charged with apredetermined quantity of a Volatile liquid, isincorporated in the cooling' unit or units in such manner, that branchesof the system propagate throughout the system the hot vapors generatedby a vapor generator.

A vapor generator, in which the volatile liquid collects before andafter defrosting operations, is included in the system. When defrostingbecomes necessary, the external application of heat to said generatorcauses the therein collected refrigerant to vaporize. The hot vaporsproduced travel upwardly and onwardly along the interiorsurfaces of thesystem, give up their heat to those surfaces, and thereby having beenliqueed, return by gravity to the generator.

The present invention, while including a vapor generator and ahermetically sealed system similar to that disclosed in saidapplication, has features and advantages not found therein.

For example, in the apparatus of the pending application, heat isapplied to the vapor generator when a defrosting operation is required.In the instant apparatus, the necessary heat is available at all timesfor instant use.

9 Claims. (Cl. (i2-115) In other words, the present vapor generator issubmerged in a eutectic or heat-holding solution sealed within aninsulated container. During compressor operations, this liquid is heatedby means of the compressor discharge line passing through said tank.

During the defrosting cycle, when, in the present method, the compressordoes not operate, the solution is continually heated by electricalmeans.

Thus, an accumulated or stored quantity of heat is at all timesavailable for the vapor generator, so, that immediate defrosting may behad when desired, and the temperature of the stored or banked heat isnot permitted to dissipate during defrosting.

Obviously, with an arrangement of this character, the invention includesmeans whereby the volatile liquid is prevented from returning to thevapor generator following a defrost operation.

The invention also provides a solenoid operated valve permittingimmediate ingress of said uid into the generator with the shutting offof the compressor, and the simultaneous energization of the heatingelement.

yOne of the features of the invention is its adaptability to anyrefrigeration system wherein a compressor is included, provided a sourceof electrical energy for operating the solenoid valve and the heater isavailable.

Particularly, though not at all exclusively, the apparatus hereof ishighly efficient in connection with 10W temperature refrigerated rooms,such as food lockers, ice cream hardening rooms, and perishablecommodity storage rooms.

Further, the invention may be incorporated, with equal eiciencyofoperation, in cooling units of the nned coil type as well as of theplate type.

Advantages and features not hereintofore set forth, should be apparent,or will be specifically noted in the description to follow, referencebeing had also to the accompanying drawing, in which the application ofmy method to a coil type, and also to a plate type evaporator unit, isillustrated.

In said drawing:

Fig. 1 is a diagrammatical illustration of a defrosting systemincorporating the invention, shown in association with an evaporatorinstallation of a refrigerated room;

Fig. 2 is a longitudinal central sectional view of a solenoid valve andelements adjacent thereto;

Fig. 3 is an end view, partly in vertical section,

of a header assembly which constitutes the preferable vapor generatorconstruction;

Fig. 4 is a ver-tical sectional view of a cooling Fig. 5 is a similarview of a cooling unit of thev plate type;

Fig. 6 is an enlarged fragmentary view, partly in section, illustratingthe closed end construction of certain tubes and conduits. f

With particular reference now to Fig. 1, numeral I0. indicates generallyan evaporator or cooling unit which may be of the coil type providedwith ns, or of the plate type. 'I'he evaporator I0 is shown suspendedfrom the ceiling of a refrigerated room, fragmentarily indicated inbroken lines and designated by the numeral I2.

Beneath the evaporator there is disposed the usual drain pan I4,provided with a drain pipe I6. A solenoid operated valve, generallydesignated I8, is interposed in a line generally indicated 20, whichextends between the evaporator I0 and a vapor generator assemblygenerally designated 22.

A condenser and a compressor included in the refrigeration system aredesignated 24 and 26 respectively, and the compressor discharge line isidentified by numeral 28.

The evaporator or cooling unit I0 may be of the type illustrated inFigs. 4 or 5. For the present, the Fig. 4 unit will be considered. It isseen to include a conventional refrigerant coil 30, provided with inletand outlet lines 32 and 34 respectively, as is understood. The drain panI4 therebeneath disposed may be supported in any well-known manner.

Brazed or welded to the coil 30 at spaced intervals, are the usual heatabsorption plates or fins 36. In normal operations, frost forms andaccumulates on the exterior of the coil and ns exposed to moisture inthe refrigerated space, and it is this frost which requires removal fromtime to time for efficient operation of the refrigeration system, as iswell understood.

The valve I8 is illustrated in detail in Fig. 2, wherein it is seen toinclude a housing or casing 38 provided with an upper chamber 40, and alower` chamber 42. A wall 44 separates said chambers, and has formedtherein a tapered seat 46 for a valve member 48.

Normally, this valve is closed. That is to say valve member 48 seatsitself by gravity. However, as will appear, when the solenoid coil 50 isenergized by the closing of manual switch 52, the valve member 48 willbe elevated to establish fluid communication between chambers 40 and 42.

The solenoid valve I8 mai7 be of any well known design, it beingrequisite only that the opening 54 in the casing 38, through which thestem thereof extends, be hermeticallysealed.

The line generally designated 20, includes an upper conduit or tube 56,and a lower conduit or tube 58, each leading to and from the valve I8,tube 56 being in communication with upper chamber 40, tube 58 with lowerchamber 42.

The invention also includes means for heating the drain pipe I6. Thus,for example, at-a region adjacent the drain pan I4, the tube 56 iscoiled about said pipe as suggested at 60, whence said tube extendsupwardly and then laterally, as at 62, to terminate in a closed end 84.

As shown in Fig. 4 the laterally extending portion 62 preferably passesthrough the upper portion of each of the fins 36, and a first branchline 66, extending laterally from tube 56, preferably passes through thelower portion of each of said iins.

2,526,032 I l l In addition, a second laterally extending branch line 68is in contact with the drain pan I4. Each branch line terminates in aclosed end 64.

As illustrated. in Fig.' 1, tube or conduit 58 terminates in adownwardly inclined portion 10 in communication with a horizontallydisposed header 12 included in the vapor generator 13.

With reference also to Fig.` 3, it is seen that said generator mayinclude one or more depending tubes 14, each having a closed end 16, andeach preferably of a reversely curved conguration as shown. A series ofplates, or heat-collecting ns 18, is provided for each tube 14, saidfins being rigidly secured thereto at intervals as shown.

It should here be noted that the precise construction of the vaporgenerator may be varied from the form shown, although the illustratedembodiment is highly efficient.

As shown in Fig. 1, the vapor generator is submerged in a eutecticsolution indicated a: which is contained within a hermetically sealedtank 80. The latter is enclosed in a layer or layers of insulatingmaterial 82, obviating loss of heat from within the tank.

The hot discharge line 28, leading from compressor 26 to condenser 24,passes through tank 80 and the liquid Withinysaid tank, a coil 84 isformed in said line, so that heat from the hot gases passingtherethrough may be more completely transferred to the solution r.

Also submerged in said solution is a suitable electric heating device86. Preferably, the heater 86 is in a circuit leading from a powersource, and including lines 88 and 90, switch 52, lines 92 and 94,solenoid 50, and leads 96 and 98. Thus it should be manifest, that whenswitch 52 is closed, both the solenoid coil and the heating device 86will simultaneously be energized.

That portion of line 20, namely tube 58 and its downwardly inclinedterminal length 10, ex-

tending between valve I8 and the vapor generator assembly 22, is coveredwith suitable insulation .99, as shown.

In iiuid communication at its lower end with tube 58, and at its upperend with what m'ay be termed the uppermostzone of the defrost apparatus,is a vapor tube |00, the provision of which between valve I8 andgenerator 13 is important, as will appear.

It is noted that, though not requisite, the condenser, the compressor,and the generator assembly, are all preferably located exteriorly of the`refrigerated space.

The cooling unit, or evaporator I0, may be of the plate type, ashereinbefore stated. In that case, as portrayed in Fig. 5, therefrigerant coil 30 is located interiorly of a hermetically sealedmetallic casing |02. Conduit 56 leads into said casing, but the lateralbranches 62 and 66 are dispensed with. Branch line 68 for the 'drain panis retained, as shown. c

From the foregoing it should be apparent that the invention includes ahermetically sealed system of hollow components comprising, inconnection with a finned type evaporator, the generator 13, line 20,valve housing 38, vapor tube |00, and laternal branches 62, 66, and 68.

In connection with a plate type evaporator, the hermetically sealedsystem includes generator 13, line 20, valve housing 38, vapor tube |00,casing |02, and lateral* branch 68.

In each case, the integrated system thus provided, is first evacuated bythe application of suction, and is thereafter charged with apredetermined quantity of refrigerant, which may be Freon, for example,or an analogous volatile liquid. Thereupon the opening, to which thesuction had been applied and thereafter the charge had been introduced,is sealed.

As will appear, in accordance with the present method, this entirecharge is contained within that portion of the system to the left ofsolenoid valve I8 during normal refrigeration operations, and flows bygravity into the vapor generator during defrosting operations.Therefore, the quantity of volatile liquid in the system is predicatedupon the aggregate volume of header 12 and tubes 14. In the drawing, theapproximate level of this liquid, designated y, when to the left of thevalve, is suggested in Figr5.

Assuming that the refrigeration system is in normal operation, hotdischarge gases passing from the compressor to the condenser via line 28give up their heat to the liquid The coil 84 in said line is providedfor increased heat transfer, as is understood. Dissipation of the heatthus obtained is obviated by the insulation 82 surrounding the tank 80,and the insulation 99 about conduit B. In other words, the arrangementis such that the heat accumulates and is stored in the tank.

At this time switch 52 is open, so that heater 86 is non-operative, andvalve 48 is seated by gravity against valve seat 44. Vapor generator 13,submerged in the eutectic solution x, ob-

viously is also hot. Therefore, any of the volatile liquid y which hadbeen trapped within the system to the right of valve I8 at the close ofa previous defrosting operation, will have vaporized and passed throughvapor line |00 into the uppermost portion of the system.

That is to say, shortly after normal operation is resumed, all of therefrigerant yvwithin the system will be confined to the left of valveI6, as will be more clearly explained.

Assuming now that the evaporator requires defrosting, the compressor isturned off and switch 52 is closed. Energization of the solenoid coil 50elevates valve 48 from its seat,v whereupon the liquid y in chamber 40and in the system to the left thereof, quickly i'lows into the vaporgenerator 13. Simultaneously, heating device 86 is energized so thatadditional heat is supplied duringv the entire defrosting cycle.

As the refrigerant y now collects in the already hot generator 13, itquickly vaporizes. The hot vapors under pressure rise and travel alongthe inner surfaces of the system, give up their heat to the evaporatorand drain pan to defrost the same, and having thereby become condensed,or liquefied, return by gravity to the generator.

It is noted that the present system does not operate on thethermo-syphon principle, since the remote ends of the various tubes areclosed as shown particularly in Fig. 6 at 64.

In other Words, thehotvapors do not circulate in the thermo-syphonsense, but rather do they permeate the system and then in reliquef'ledform, return to the generator by gravity along the same passages theypreviously traveled in vapor form. This action is diagrammatically il.lustrated in connection with Fig. 6, wherein the arrows indicate vapors,and the letter y the condensed refrigerant returning to the generator.

The defrosting cycle continues as long as switch 52 remains closed. Mostof the vapors generated iiow upwardly through line 20 into the branches62, 66, and 68. Some vapors also ow through tube I 00 into the uppermostregion of the system.

Since branches 62 and 66 are in intimate contact with each of the iins36, diffusion of heat throughout the evaporator parts is rapid.

At the same time, since branch 68 is in intimate contact with drain panI4, quick heat conduction to the latter is had. Coils 66 about drainpipe I6 obviate the necessity of any separate or special device topervent drippings from freezing.

Obviously, a defrostingoperation continues until all of the accumulatedfrost on the evaporator assembly has been melted. The fins 18 areprovided on the generator tubes 14 to more quickly transfer the heatfrom the liquid a: to the liquid y. Device 86 continuously replaces theheat withdrawn by the generator.

Should the cooling unit be of the plate type, the defrosting cycleoperates in identical fashion. In such case, the casing |02 performs thefunction of branches 62 and 66, so that the accumulated frost on theexterior surfaces of said casing are caused to melt.

Assuming now that defrosting is complete, switch 52 is thrown open, thecompressor is turned on, and normal refrigeration resumes.Simultaneously with the opening of switch 52, valve 48 drops into itsseat, thereby preventing all the liquid yin the system to the left ofthe valve from returning again to the generator.

However, it is apparent that concurrently some of the liquid y will beon its way to lche generator in conduit 58. Since the accumulated heatin tank has been continually replenished by the heating device 86, allthe liquid in the system to the right of the valve will continue tovaporize and pass through tube I 0I) into the uppermost region of thesystem, whence it joins the body of liquid already trapped to the leftof the valve.

From the foregoing, it is manifest that a novel method, and apparatusfor performing the method, has been provided. A defrosting operation maybe initiated quickly, since an ever present quantity of heat isavailable. In addition, because of this arrangement, complete defrostingrequires only a short time, so that no appreciable temperature rise inthe refrigerated space will result.

Although not illustrated, it should be evident that a single vaporgenerator assembly 22 of proper proportion may serve to defrost aplurality of evaporators. Also that the solenoid valve, the heatingdevice, and the compressor may all be in the same, or in separatecircuits.

The particular embodiment illustrated and described is obviouslysusceptible of modification without departing from the principles of theinvention.

For example, the eutectic solution may be heated by a hot Water coilimmersed therein, instead of by the compressor discharge line, ifdesired. Further, instead of said eutectic solution, the tank 80 maycontain water or other liquid maintained at a high temperature by anysuitable means. Thus, for example, assuming that the tank 80 doescontain water, it should be apparent that a constant or an intermittentiiow of hot water into and out of said tank would produce the sameresult as that produced by the compressor discharge line, the hot watercoil, and so on. I

Therefore, it is to be understood that the invention is not to belimited to the precise details illustrated and described.

What I claim is:

` l. The method of defrosting an evaporator which consists intransferring the heat from the compressor discharge line to a eutecticsolution contained in a hermetically sealed tank and preventing thedissipation of said heat during normal refrigerating operations,subjecting a predetermined quantity of volatile liquid to the action ofsaid heat during a defrost operation, providing means for transmittingthe hot vapors thus generated to the evaporator for condensation andreturn to the heat supply, and providing electrical means forcontinuously replenishing the heat withdrawn from said supply duringeach defrosting cycle.

2. Apparatus for defrosting an'evaporator and its associated drain pan,said apparatus including an integrated system of hollow components whichafter having rst been evacuated has thereafter been charged with apredetermined quantity of volatile liquid sealed therein, a vaporgenerator remote from the evaporator and in fluid communication withsaid system, a hermetically sealed heat storage tank containing a supplyof eutectic in which said generator is submerged, a coil formed in thedischarge line of a compressor and submerged in the eutectic to heat thesame, and a covering of insulation about said tank to prevent the escapeof accumulated heat therefrom.

3. Apparatus for defrosting an evaporator and its associated drain pan,including an integrated system of hollow components which after havingrst been evacuated has thereafter been charged with a predeterminedquantity of volatile liquid sealed therein, a vapor generator remotefrom the evaporator and in fluid communication with said system, ahermetically sealed heat storage tank containing a supply of eutectic inwhich said generator is submerged, a coil formed in the discharge lineof a compressor and submerged in the eutectic to heat the same, acovering of insulation about said tank to prevent the escape ofaccumulated heat therefrom, a normally nonoperating heating element alsosubmerged in said eutectic, a solenoid operable valve for normallyconiining the secondary refrigerant within a portion of the systemremote from said generator, and .means for energizing said heatingelement and solenoid during a defrost operation.

4. The apparatus of claim 3 in which the integrated system of hollowcomponents includes said vapor generator, said solenoid operable valve,a rst conduit leading from the valveV to the generator, a second conduitleading from the valve to the evaporator and terminating in a laterallyextending portion in intimate contact with elements of said evaporator,a rst laterally extending branch also in intimate contact withelementspf said evaporator, a second laterally extending branch inintimate contact with said drain pan, said laterally extending portionand said branches being provided with closed ends, coils formed in thesecond conduit about the drain pipe associated with said drain span, anda vapor line the lower end of which is in fluid cornmunication with therst conduit, and the upper end of which is in communication with aportion of said system in the uppermost zone thereof.

5. The apparatus of claim 3 in which the integrated system of hollowcomponents includes said vapor generator, said solenoid operable valve,a first conduit leading from the valve to the generator, a secondconduit leading from the valve to the casing of a plate type evaporator,a laterally extending branch in intimate contact with said drain pan andbeing provided with a closed end, coils formed in the second conduit andabout the drain fpipe associated with said drainpan, and a vapor linethe lower end of which is in fluid communication with the first conduit,and the upper end of which is in communication with said casing at thetop thereof.

6. In a defrosting apparatus of the character described. a vaporgenerator assembly including a hermetically sealed tank, a quantity ofeutectic therein, a covering of insulation enclosing the tank, agenerator submerged in the eutectic, an electrically operable heatingdevice submerged in the eutectic, means for controlling the operation ofsaid heating device, and means for heating said eutectic during normalrefrigeration operations.

7 In a defrosting apparatus of the character described, a vaporgenerator assembly including a hermetically sealed tank, a quantity ofeutectic therein, a covering of insulation enclosing the tank, agenerator submerged in the eutectic, an electrically operable heatingdevice submerged in the eutectic, means for controlling the operation ofsaid heating device, and means for heating said eutectic during normalrefrigeration operations, said means comprising a line leading from thecompressor to the condenser and passing through said tank whereby theheat inherent in the hot gases flowing through said line is absorbed bythe eutectic.

8. In a defrosting apparatus of the character described, a vaporgenerator including a header, a conduit leading therefrom, one or morereversely curved tubes depending from the header and each terminating ina cosed lower end, and a series' of heat-absorbing fins rigidly attachedto each tube at intervals throughout its length, said header, conduit,and tubes being immersed in a body of liquid maintained at a hightemperature within a hermetically sealed tank.

9. ,In a secondary defrosting system of the character described, a vaporgenerator including a header, one or more tubes depending from theheader and each terminating in a closed lower end, a series ofheat-absorbing ns rigidly attached to each tube at intervals throughoutits length, a conduit leading from the header to a valve selectivelyoperable to permit or prevent flow of the vapors generated to thatportion of said system located in proximity to an evaporator, saidheader, tubes, and a portion of said conduit being immersed in a body ofliquid maintained at .a high temperature within a tank not located inproximity to said evaporator, and a vapor tube the upper end of whichopens into a portion of said system inthe upper zone thereof, the lowerend of which opens into a portion of said system in the lower zonethereof.

LOUIS F. LA PORTE.

REFERENCES CITED The following references are of record in the le oi'this patent:

UNITED STATES PATENTS Number Name Date 1,890,085 Hill Dec. 6, 19321,912,841 Haymond June 6, 1933 1,937,288 McGraw Nov. 28, 1933 2,081,479Fink May 25, 1937 2,095,017 Wilkes et al. Oct. 5, 1937 2,181,276 Kogelet al Nov. 28, 1939 2,286,205 Grubb June 16, 1942 2,452,102 CocanourOct. 26, 1948

